This invention relates to a sound source apparatus capable of generating a desired tone and producing a musical sound fairly close to the natural sound produced by a musical instrument.
A variety of ways of producing artificial sounds have been hitherto proposed. According to one of these conventional sound generating ways a sinusoidal fundamental wave and its harmonic waves are generated and these waves are selectively combined with each other to produce a desired tone. According to another conventional way a sawtooth or square wave containing a great number of harmonic waves is generated, and selected harmonic waves are eliminated from the sawtooth or square wave to simulate a desired tone. According to still another conventional way a variety of sound waves are stored and are selectively used. These conventional methods, however, produce sounds of fixed waveforms, and therefore the resultant tone causes a somewhat stiff sensation in the ear. In an attempt to produce profound, rich artificial tones, in the first conventional method the selected harmonic to fundamental wave ratio is varied with time; in the second conventional method the characteristics of filters are varied with time, thereby changing harmonic contents with time; and in the third and final conventional method the mixing ratio of different sound waves is varied, or otherwise the speed at which sound waves are picked is varied with time.
Electronic musical instruments and synthesizers produce different tones in such ways as mentioned above. In case of adding the fundamental wave and its harmonic waves to each other, or in case of subtracting harmonics from a given waveform it is difficult to produce different tones or sounds such as would be produced by different types of musical instruments, and there is the tendency of producing noise in the course of addition or subtraction proceedings, and deteriorating the sound quality. Also, there is a problem of difficulty in producing a delicate or characteristic variation of sound, such as an impressive sensation in the ear at the beginning part of a blow on the trumpet.